The use of polyurethane foam or similar formulations as packing material has become widespread for a number of reasons, including its relative low cost, ease of molding into desired cross-sectional configuration to match the contour of an article being packaged or transported, and its ability to withstand shock loads to protect such an article. Normally, the person designing the package or packing unit is required to select a foam density which is sufficient for properly supporting the portions of the article at which maximum loading conditions are present, even though this results in a foam mass having an excessively high density adjacent other portions of the article. Since the packing unit manufacturing cost is dependent in part on the density of the foam being used, a wasteful situation prevails; additionally the higher density foam results in a greater than necessary weight for the packing unit, resulting in added shipping costs.